1. Field of the Invention
The present invention relates to a combination MR (magnetoresistive)/inductive thin film magnetic head carried on, for example, a hard disk drive, and particularly to a thin film magnetic head in which materials of an upper core layer and a lower core layer are improved to improve magnetic characteristics, and a manufacturing method thereof.
2. Description of the Related Art
FIG. 15 is an enlarged sectional view showing a conventional thin film magnetic head as viewed from the side thereof opposite to a recording medium.
This thin film magnetic head comprises a reading head h1 which employs the magnetoresistive effect and a writing inductive head h2, which are laminated on the trailing-side end surface of a slider which constitutes, for example, a floating head.
The reading head h1 comprises a lower shielding layer 1 made of sendust, an Nixe2x80x94Fe alloy (permalloy) or the like, a lower gap layer 2 made of a non-magnetic material such as Al2O3 (aluminum oxide) or the like and formed on the lower shielding layer 1, and a magnetoresistive element 3 deposited on the lower gap layer 2. The magnetoresistive element 3 comprises three layers including a soft adjacent layer (SAL), a non-magnetic layer (SHUNT layer), and a magnetoresistive layer (MR layer) which are laminated in turn. Generally, the magnetoresistive layer comprises an Nixe2x80x94Fe alloy (permalloy) layer, the non-magnetic layer comprises a tantalum layer, and the soft adjacent layer comprises an Nixe2x80x94Fexe2x80x94Nb alloy layer.
On both sides of the magnetoresistive layer 3 are formed hard bias layers serving as longitudinal bias layers. On the hard bias layers are formed main lead layers 5 made of a non-magnetic conductive material having low electric resistance, such as Cu (copper), W (tungsten) or the like. On the main lead layers 5 is further formed an upper gap layer 6 made of a non-magnetic material such as aluminum oxide or the like.
On the upper gap layer 6 is formed a lower core layer 20 by plating permalloy. In the inductive head h2, the lower core layer 20 functions as a leading-side core portion which gives a recording magnetic field to a recording medium. In the reading head h1, the lower core layer 20 functions as an upper shielding layer, and a gap length G11 is determined by the gap between the lower shielding layer 1 and the lower core layer 20.
On the lower core layer 20 are laminated a gap layer (non-magnetic material layer) 8 made of aluminum oxide or the like, and an insulation layer (not shown in the drawing) made of polyimide or a resist material, and a coil layer 9 patterned to a spiral form is provided on the insulation layer. The coil layer 9 is made of a non-magnetic conductive material having low electric resistance, such as Cu (copper) or the like. The coil layer 9 is surrounded by an insulation layer (not shown) made of polyimide or a resist material, and an upper core layer 21 made of a magnetic material such as permalloy is formed on the insulation layer by plating. The upper core layer 21 functions as the trailing-side core portion of the inductive head h2 which gives a recording magnetic field to the recording medium.
As shown in FIG. 15, on the side opposite to the recording medium, the tip 21a of the upper core layer 21 is opposed to the upper side of the lower core layer 20 with the gap layer 8 therebetween to form a magnetic gap having a magnetic gap length G12 which gives a magnetic field to the recording medium. On the upper core layer 21 is provided a protective layer 11 made of aluminum oxide or the like.
In the inductive head h2, when a recording current is supplied to the coil layer 9, a recording magnetic field is applied to the upper core layer 21 and the lower core layer 20 from the coil layer 9. In the magnetic gap, magnetic signals are recorded on the recording medium such as a hard disk by a leakage magnetic field between the lower core layer 20 and the upper core layer 21.
FIG. 16 is an enlarged sectional view showing a conventional method of producing the lower core layer 20.
As shown in FIG. 16A, a base layer 22 made of a magnetic material such as permalloy or the like is formed on the upper gap layer 6 by plating. On the base layer 22 is coated a resist solution, followed by exposure to form rectangular resist layers 23 on the base layer 22. In FIG. 16B, magnetic material layers 20 and 24 made of permalloy or the like are formed, by plating, on portions of the base layer 22 where the resist layers 23 are not formed. The magnetic material layer 20 formed between the resist layers 23 is left behind as the lower core layer.
In FIG. 16C, the resist layers 23 are removed, and portions of the base layer 22 which are formed below the resist layers 23 are removed by ion milling. In FIG. 16D, a protective layer 25 made of a resist material is formed on the portions on the upper gap layer 6 where the resist layers 23 were removed, to cover the magnetic material layer 20. In FIG. 16E, the magnetic material layers 24 and portions of the base layer 22 which are formed directly below the magnetic material layers 24 are removed by wet etching. In FIG. 16F, the protective layer 25 is removed to leave only the rectangular lower core layer 20 on the upper gap layer 6 with the base layer 22 therebetween.
The conventional thin film magnetic head shown in FIG. 15 comprises the lower core layer 20 formed by plating permalloy and thus has the following problems.
(i) Since the lower core layer 20 (the upper shielding layer) is thick and has a substantially rectangular sectional shape, step portions A each having a corner are formed at both side ends of the lower core layer 20. Therefore, it is difficult to form the gap layer 8 having a uniform thickness on the lower core layer 20. Particularly, the thickness of the gap layer 8 is extremely small near the corners of the step portions A at both side ends of the lower core layer 20, and thus an insulation failure easily occurs between the lower core layer 20 and the coil layer 9.
Also, in order to increase the recording density, it is necessary to thin the gap layer 8 to decrease the gap length G12 of the magnetic gap. However, when the gap layer is thinned, pin holes easily occur in the gap layer 8 near the step portions A.
(ii) Since the lower core layer 20 (the upper shielding layer) has a rectangular sectional shape, and the step portions A are formed at both side ends thereof, a difference in height is also formed in the surface of the gap layer 8 formed on the step portions A. Therefore, when the area of the lower core layer 20 is smaller than the region of the coil layer 9, the coil layer 9 is formed on the step portions of the gap layer 8, thereby making it difficult to form the coil layer 9 and easily causing defects in the coil layer 9.
(iii) In order to increase the recording density of signals on the recording medium, and increase the magnetic writing frequency, it is necessary to improve the soft magnetic characteristics of the lower core layer 20 and the upper core layer 21 to impart low coercive force and high resistivity thereto. Although the saturation magnetic flux density is preferably as high as possible, particularly when the saturation magnetic flux density of the lower core layer 20 is lower than that of the upper core layer 21 so that magnetization of a leakage magnetic field between the lower core layer 20 and the upper core layer 21 is easily reversed, the density of signal writing on the recording medium can possibly be increased.
In the thin film magnetic head shown in FIG. 15, since the lower core layer 20 functions not only as a leading-side core portion for the inductive head h2 but also as an upper shielding layer for the reading head h1, the lower core layer 20 must be provided with both the properties as a core and the properties as a shield.
In order to improve the shielding function of the lower core layer 20, the direction (the direction perpendicular to the drawing of FIG. 15) of an external magnetic field applied from the recording medium is preferably the direction of the hard axis of magnetization, the saturation magnetic flux density is not excessively high, and the lower core layer 20 preferably has low coercive force and a low magnetostriction constant in order to prevent excessive increase in the saturation magnetic flux density.
Also, in order to further increase the density of signal recording on the recording medium, it is necessary to improve the soft magnetic characteristics of the lower core layer 20 and the upper core layer 21, and decrease the gap length G12 of the magnetic gap in the inductive head h2. Therefore, the non-magnetic material layer 8 is formed to be as thin as possible.
Further, in the reading head h1, in order to improve the resolution of the leakage magnetic field from the recording medium subjected to high-density recording, it is necessary to decrease the gap length G11 of the magnetic gap. Therefore, the lower gap layer 2 and the upper gap layer 6 are formed to be as thin as possible.
However, even if the magnetic gap is decreased, when the shielding function of the lower core layer 20 deteriorates, the MR layer of the magnetoresistive element layer 3 cannot be shielded from recording noise of the recording medium and thus captures excess signals, thereby causing the problem of easily producing Barkhausen noise.
As described above, the lower core layer 20 having both the leading-side core function for the inductive head h2 and the upper shielding function for the reading head h1 is preferably made of a soft magnetic material having a lower saturation magnetic flux density than the upper core layer 21, low coercive force, high resistivity and a low magnetostriction constant.
However, permalloy which forms the conventional lower core layer 20 and upper core layer 21 has a relatively high saturation magnetic flux density of 1.0 T (tesla) and coercive force of as low as 0.5 Oe (oersted) in the direction of hard axis, but has a resistivity of as low as 30 (xcexcxcexa9xc2x7cm). Therefore, when the recording frequency is further increased, an eddy current occurs in the lower core layer 20 and the upper core layer 21, and thus a heat loss due to the eddy current is increased. Also the magnetic permeability in a high frequency region deteriorates, thereby deteriorating the shielding function and easily producing Barkhausen noise in the MR layer.
U.S. Pat. No. 5,573,863 discloses s soft magnetic material comprising a mixture of a bcc-structure Fe fine crystalline phase and an amorphous phase containing an element selected from the rare earth elements, Ti, Zr, Hf, V, Nb, Ta and W, and O. The composition ratios of the soft magnetic material can be appropriately adjusted to obtain a high saturation magnetic flux density, low coercive force and high resistivity. Therefore, the use of the soft magnetic material for the lower core layer 20 and the upper core layer 21 enables manufacture of a thin film magnetic head having excellent magnetic characteristics.
With this soft magnetic material, a film cannot be formed by plating, but can be formed only by a sputtering method or an evaporation method. However, a conventional method of manufacturing a thin film magnetic head is difficult to form the lower core layer 20 by the sputtering method or evaporation method. The reasons for this will be described below.
When the lower core layer 20 is formed by the sputtering method, a layer of the soft magnetic material is formed directly on the upper gap layer 6 made of aluminum oxide or the like. However, in order to form the soft magnetic material layer in a predetermined shape, unnecessary portions must be removed by ion milling (dry etching). However, ion milling for removing the soft magnetic material layer causes the problem of damaging the upper gap layer 6 made of aluminum oxide formed below the soft magnetic material layer.
Although the upper gap layer is formed to a thickness of about 1000 angstroms, the lower core layer is formed to a larger thickness than the upper gap layer. It is generally thought that ion milling for removing a predetermined thickness causes a tolerance of about 5% for a thickness which can be removed. Therefore, ion milling for removing a predetermined portion of the lower core layer makes the thin upper gap layer formed below the lower core layer easy to damage due to the tolerance of about 5% for the thickness removed.
For the above described reasons, the lower core layer 20 is removed by ion milling, and at the same time, the upper gap layer 6 is partly removed. In the worst case, the entire upper gap layer 6 is removed, and thus the main lead layer 5 formed below the upper gap layer 6 is affected by ion milling.
A first object of the present invention is to solve the above problems of conventional magnetic heads, and provide a thin film magnetic head in which the soft magnetic characteristics of an upper core layer and a lower core layer are improved by appropriately adjusting the composition ratios of a soft magnetic material disclosed in, for example, U.S. Pat. No. 5,573,863 to agree with the properties required for the lower core layer and the upper core layer.
A second object of the present invention is to provide a thin film magnetic head and a manufacturing method thereof comprising a shielding layer formed on a magnetoresistive element layer with an insulation layer therebetween so that at both ends of the shielding layer, the thickness gradually decreases, whereby a coil layer can be stably formed on the shielding layer with an insulation layer therebetween, and insulation characteristics of the shielding layer and the coil layer can be stabilized.
A third object of the present invention is to provide a thin film magnetic-head and a manufacturing method thereof, comprising a shielding layer which can be formed by a vacuum deposition method such as a sputtering method or an evaporation method so as to increase the degree of selectivity of a soft magnetic material used for the shielding layer and cope with high frequency recording and high density recording.
In order to achieve the objects of the present invention, the present invention provides a thin film magnetic head comprising a magnetoresistive element layer, a main lead layer for supplying a sensing current to the magnetoresistive element layer, a lower core layer formed on the main lead layer with an insulation layer therebetween and having both a leading-side core function for an inductive head and an upper shielding function for a reading head, an upper core layer opposed to the lower core layer with a magnetic gap therebetween in the portion opposite to a recording medium, and a coil layer for applying a magnetic field to both core layers; wherein the upper core layer is made of a soft magnetic material having:
a composition expressed by the formula FeaMbOc wherein M indicates at least one element elected from Al, Si, Hf, Zr, V, Nb, Ta, W, Mg and the rare earth elements; and composition ratios a, b and c (atomic %) are adjusted to obtain a saturation magnetic flux density of 1.3 T (tesla) or more and a coercive force of 1.0 Oc (oersted) or less in the direction of hard axis.
When the upper core layer is made of an FeaMbOc alloy, in a ternary diagram of the FeaMbOc alloy in which the composition ratios of element Fe, element M and element O are shown on the respective sides, the composition ratios a, b and c (atomic %) are preferably surrounded by the following ten points.
A (Fe:M:O)=(52.5:12.5:35.0)
B (Fe:M:O)=(53.3:11.1:35.6)
C (Fe:M:O)=(57.5:9.0:33.5)
D (Fe:M:O)=(63.3:4.8:31.9)
E (Fe:M:O)=(75.3:4.0:20.7)
F (Fe:M:O)=(76.3:5.0:18.7)
G (Fe:M:O)=(75.0:6.7:18.3)
H (Fe:M:O)=(70.0:9.0:21.0)
I (Fe:M:O)=(57.4:13.0:29.6)
J (Fe:M:O)=(53.5:13.0:33.5)
For example, when the upper core layer is made of a an FeaHfbOc alloy as an example of FeaMbOc alloys, in a ternary diagram of the FeaHfbOc alloy in which the composition ratios of element Fe, element Hf and element O are shown on the respective sides thereof, the composition ratios a, b and c (atomic %) are preferably surrounded by the following ten points:
A (Fe:Hf:O)=(52.5:12.5:35.0)
B (Fe:Hf:O)=(53.3:11.1:35.6)
C (Fe:Hf:O)=(57.5:9.0:33.5)
D (Fe:Hf:O)=(63.3:4.8:31.9)
E (Fe:Hf:O)=(75.3:4.0:20.7)
F (Fe:Hf:O)=(76.3:5.0:18.7)
G (Fe:Hf:O)=(75.0:6.7:18.3)
H (Fe:Hf:O)=(70.0:9.0:21.0)
I (Fe:Hf:O)=(57.4:13.0:29.6)
J (Fe:Hf:O)=(53.5:13.0:33.5)
The upper core layer may be formed of a soft magnetic material having:
a composition expressed by the formula FeaMb(T+O)c wherein M indicates at least one element selected from Al, Si, Hf, Zr, V, Nb, Ta, W, Mg and the rare earth elements, and T indicates either of B and C; and composition ratios a, b and c (atomic %) are adjusted to obtain a saturation magnetic flux density of 1.3 T (tesla) or more and a coercive force of 1.0 Oc (oersted) or less in the direction of hard axis.
When the upper core layer is made of an FeaMb(T+O)c alloy, in a ternary diagram of the FeaMb(B+O)c alloy in which the composition ratios of element Fe, element M and elements (B+O) are shown on the respective sides, the composition ratios a, b and c (atomic %) are preferably in the range surrounded by the following eight points.
A (Fe:M:B+O)=(60.0:9.5:30.5)
B (Fe:M:B+O)=(62.5:6.0:31.5)
C (Fe:M:B+O)=(66.8:4.0:29.2)
D (Fe:M:B+O)=(74.0:5.0:21.0)
E (Fe:M:B+O)=(75.0:7.5:17.5)
F (Fe:M:B+O)=(72.3:10.5:17.2)
G (Fe:M:B+O)=(62.6:13.7:23.7)
H (Fe:M:B+O)=(60.8:12.3:26.9)
For example, when the upper core layer is made of a an FeaHfb(B+O)c alloy as an example of FeaMb(T+O)c alloys, in a ternary diagram of the FeaHfb(B+O)c alloy in which the composition ratios of element Fe, element Hf and elements (B+O) are shown on the respective sides thereof, the composition ratios a, b and c (atomic %) are preferably in the range surrounded by the following eight points:
A (Fe:Hf:B+O)=(60.0:9.5:30.5)
B (Fe:Hf:B+O)=(62.5:6.0:31.5)
C (Fe:Hf:B+O)=(66.8:4.0:29.2)
D (Fe:Hf:B+O)=(74.0:5.0:21.0)
E (Fe:Hf:B+O)=(75.0:7.5:17.5)
F (Fe:Hf:B+O)=(72.3:10.5:17.2)
G (Fe:Hf:B+O)=(62.6:13.7:23.7)
H (Fe:Hf:B+O)=(60.8:12.3:26.9)
The present invention also provides a thin film magnetic head comprising a magnetoresistive element layer, a main lead layer for supplying a sensing current to the magnetoresistive element layer, a lower core layer formed on the main lead layer with an insulation layer therebetween and having both a leading-side core function for an inductive head and an upper shielding function for a reading head, an upper core layer opposed to the lower core layer with a magnetic gap therebetween in the portion opposite to a recording medium, and a coil layer for applying a magnetic field to both core layers; wherein the lower core layer is made of a soft magnetic material having:
a composition expressed by the formula FeaMbOc wherein M indicates at least one element selected from Al, Si, Hf, Zr, V, Nb, Ta, W, Mg and the rare earth elements; and composition ratios a, b and c (atomic %) are adjusted to obtain a magnetostriction constant of 1.0xc3x9710xe2x88x926 or less and a coercive force of 1.0 Oc (oersted) or less in the direction of hard axis.
When the lower core layer is made of an FeaMbOc alloy, in a ternary diagram of the FeaMbOc alloy in which the composition ratios of element Fe, element M and element O are shown on the respective sides, the composition ratios a, b and c (atomic %) are preferably in the range surrounded by the following eight points.
C (Fe:M:O)=(57.5:9.0:33.5)
D (Fe:M:O)=(63.3:4.8:31.9)
E (Fe:M:O)=(75.3:4.0:20.7)
F (Fe:M:O)=(76.3:5.0:18.7)
G (Fe:M:O)=(75.0:6.7:18.3)
H (Fe:M:O)=(70.0:9.0:21.0)
I (Fe:M:O)=(57.4:13.0:29.6)
K (Fe:M:O)=(67.5:6.7:25.8)
For example, when the lower core layer is made of a an FeaHfbOc alloy as an example of FeaMbOc alloys, in a ternary diagram of the FeaHfbOc alloy in which the composition ratios of element Fe, element Hf and element O are shown on the respective sides thereof, the composition ratios a, b and c (atomic %) are preferably in the range surrounded by the following eight points:
C (Fe:Hf:O)=(57.5:9.0:33.5)
D (Fe:Hf:O)=(63.3:4.8:31.9)
E (Fe:Hf:O)=(75.3:4.0:20.7)
F (Fe:Hf:O)=(76.3:5.0:18.7)
G (Fe:Hf:O)=(75.0:6.7:18.3)
H (Fe:Hf:O)=(70.0:9.0:21.0)
I (Fe:Hf:O)=(57.4:13.0:29.6)
K (Fe:Hf:O)=(67.5:6.7:25.8)
The lower core layer may be formed of a soft magnetic material having:
a composition expressed by the formula FeaMb(T+O)c wherein M indicates at least one element selected from Al, Si, Hf, Zr, V, Nb, Ta, W. Mg and the rare earth elements, and T indicates either of B and C; and composition ratios a, b and c (atomic %) are adjusted to obtain a magnetostriction constant of 1.0xc3x9710xe2x88x926 or less and a coercive force of 1.0 Oc (oersted) or less in the direction of hard axis.
When the upper core layer is made of an FeaMb(T+O)c alloy, in a ternary diagram of the FeaMb(B+O)c alloy in which the composition ratios of element Fe, element M and elements (B+O)are shown on the respective sides, the composition ratios a, b and c (atomic %) are preferably in the range surrounded by the following eight points.
C (Fe:M:B+O)=(66.8:4.0:29.2)
B (Fe:M:B+O)=(74.0:5.0:21.0)
C (Fe:M:B+O)=(75.0:7.5:17.5)
D (Fe:M:B+O)=(72.3:10.5:17.2)
E (Fe:M:B+O)=(62.6:13.7:23.7)
F (Fe:M:B+O)=(57.5:14.5:28.0)
G (Fe:M:B+O)=(57.8:10.2:32.0)
H (Fe:M:B+O)=(58.7:4.4:36.9)
For example, when the lower core layer is made of a an FeaHfb(B+O)c alloy as an example of FeaMb(T+O)c alloys, in a ternary diagram of the FeaHfb(B+O)c alloy in which the composition ratios of element Fe, element Hf and elements (B+O)are shown on the respective sides thereof, the composition ratios a, b and c (atomic %) are preferably in the range surrounded by the following eight points:
C (Fe:Hf:B+O)=(66.8:4.0:29.2)
B (Fe:Hf:B+O)=(74.0:5.0:21.0)
C (Fe:Hf:B+O)=(75.0:7.5:17.5)
D (Fe:Hf:B+O)=(72.3:10.5:17.2)
E (Fe:Hf:B+O)=(62.6:13.7:23.7)
F (Fe:Hf:B+O)=(57.5:14.5:28.0)
G (Fe:Hf:B+O)=(57.8:10.2:32.0)
H (Fe:Hf:B+O)=(58.7:4.4:36.9)
Both the upper core layer and the lower core layer may be formed of a soft magnetic material having a composition expressed by the formula NiaFebXc wherein X indicates either of Mo and S, and the composition ratios a, b and c by atomic % satisfy the following relations:
44xe2x89xa6axe2x89xa654, 42.5xe2x89xa6bxe2x89xa654.0, 0xe2x89xa6cxe2x89xa64, a+b+c=100.
The Fexe2x80x94Mxe2x80x94O alloy and Fexe2x80x94M-(T+O) alloy are soft magnetic materials comprising a mixture of an Fe fine crystalline phase and an amorphous phase containing M and O at higher concentrations than the Fe crystalline phase; and films thereof are deposited by a vacuum deposition method such as the sputtering method or the evaporation method. Films of Nixe2x80x94Fexe2x80x94X alloys are formed by plating.
In the present invention, the Fexe2x80x94Mxe2x80x94O alloy or Fexe2x80x94M-(T+O)alloy in which the composition ratios are appropriately adjusted to obtain a saturation magnetic flux density of 1.3 T (tesla) or more and a coercive force of 1.0 Oe (oersted) or less in the direction of hard axis is used for the upper core layer. The Fexe2x80x94Mxe2x80x94O alloy and Fexe2x80x94M-(T+O) alloy having a saturation magnetic flux density of 1.3 T (tesla) or more and a coercive force of 1.0 Oe (oersted) or less in the direction of hard axis have a resistivity of 100 xcexcxcexa9xc2x7cm or more.
The upper core layer may be formed of an Nixe2x80x94Fexe2x80x94X alloy in which a saturation magnetic flux density of 1.3 T (tesla) or more and a coercive force of 1.0 Oe (oersted) or less in the direction of hard axis can be obtained by appropriately adjusting the composition ratios. However, the resistivity of this alloy is about 45 to 75 xcexcxcexa9xc2x7cm which is lower than the Fexe2x80x94Mxe2x80x94O alloy and Fexe2x80x94M-(T+O) alloy.
In the present invention, the Fexe2x80x94Mxe2x80x94O alloy or Fexe2x80x94M-(T+O)alloy in which the composition ratios are appropriately adjusted to obtain a magnetostriction constant of 1.0xc3x9710xe2x88x926 or less and a coercive force of 1.0 Oe (oersted) or less in the direction of hard axis is used for the lower core layer having both the core function and the shielding function. The Fexe2x80x94Mxe2x80x94O alloy and Fexe2x80x94M-(T+O) alloy having a magnetostriction constant of 1.0xc3x9710xe2x88x926 or less and a coercive force of 1.0 Oe (oersted) or less have a saturation magnetic flux density of 0.7 T or more, and a resistivity of 100 xcexcxcexa9xc2x7cm or more.
The lower core layer may be formed of an Nixe2x80x94Fexe2x80x94X alloy in which a saturation magnetic flux density of 0.7 T (tesla) or more and a coercive force of 1.0 Oe (oersted) or less in the direction of hard axis can be obtained by appropriately adjusting the composition ratios. However, the resistivity of this alloy is about 45 to 75 xcexcxcexa9xc2x7cm which is lower than the Fexe2x80x94Mxe2x80x94O alloy and Fexe2x80x94M-(T+O) alloy.
As described above, the Fexe2x80x94Mxe2x80x94O-alloy, Fexe2x80x94M-(T+O) alloy and Nixe2x80x94Fexe2x80x94X alloy have a high resistivity value and thus hardly produce an eddy current even when the recording frequency is increased, and exhibit high magnetic permeability at high frequency.
Therefore, the Fexe2x80x94Mxe2x80x94O-alloy, Fexe2x80x94M-(T+O) alloy and Nixe2x80x94Fexe2x80x94X alloy are soft magnetic materials which can satisfy the properties required for the lower core layer and the upper core layer. Thus, when any one of these three types of soft magnetic materials in which the composition ratios are appropriately adjusted is used for the lower core layer and the upper core layer, a thin film magnetic head which can cope with high-density recording and high-frequency recording can be manufactured.
In the thin film magnetic head of the present invention comprising the reading head having the magnetoresistive element layer, and the inductive head laminated on the reading head and comprising the coil layer and the core layer, the shielding layer is formed on the magnetoresistive element layer with an insulation layer therebetween so that the thickness thereof is substantially uniform and gradually decreases toward both side ends thereof.
Also an anti-milling layer made of a non-magnetic material is preferably formed on either side of the shielding layer. The formation of the anti-milling layers prevents breakage of the insulation layer (the upper gap layer) formed below the shielding layer even by ion milling in formation of the shielding layer.
The material for forming the anti-milling layers preferably has a milling rate lower than that of the material for forming the shielding layer.
The present invention also provides a method of manufacturing a thin film magnetic head comprising a reading head having a magnetoresistive element layer and an inductive head laminated on the reading head and comprising a coil layer and a core layer, the method comprising forming a shielding layer on the magnetoresistive element layer with an insulation layer therebetween by a method comprising the steps of:
forming a resist layer for a lift off method on the insulation layer;
forming an anti-milling layer made of a non-magnetic material on the surface of the resist layer for the lift off method and a portion of the insulation layer where the resist layer for the lift off method was not formed;
removing the resist layer for the lift off method;
forming a soft magnetic material layer on the portion of the insulation layer where the resist layer for the lift off method was removed, and on the anti-milling layer by sputtering or evaporation;
a forming a resist layer on the portion of the insulation layer where the resist layer for the lift off method was removed, with the soft magnetic material layer therebetween;
removing the soft magnetic material layer by ion milling, leaving as a lower core layer the portion of the soft magnetic material layer formed below the resist layer; and
removing the resist layer formed on the lower core layer.
At the bottom of either side end of the resist layer for the lift off method is preferably formed a slope.
The anti-milling layer is preferably formed to a thickness of about 3000 angstroms.
The ion milling rate of the material which forms the anti-milling layer is preferably lower (smaller) than that of the material which forms the shielding layer. More preferably, the milling rate ratio of the shielding layer to the anti-milling layer is 2 or more.
In the present invention, since the shielding layer is formed so that the thickness at either end thereof gradually decreases, it is possible to eliminate the step portions at both ends of the lower core layer (the shielding layer), which are formed in the conventional example shown in FIG. 15, stabilize the shape of the coil layer, form the gap layer having a uniform thickness on the lower core layer, and stabilize the insulating function of the gap layer.
Also, since the shielding layer can be formed by the vacuum deposition method such as the sputtering method or the evaporation method, the selectivity of the soft magnetic material used for forming the shielding layer can be widened. For example, when the shielding layer has both the core function and the shielding function, a thin film magnetic head which hardly generate an eddy current even if the frequency is increased can be manufactured by using a soft magnetic material having excellent magnetic characteristics such as a high saturation magnetic flux density, low coercive force, high resistivity, etc., as disclosed in U.S. Pat. No. 5,573,863.
In the method of forming the shielding layer, the resist layer for the lift off method is first formed on the upper gap layer, and the anti-milling layers made of aluminum oxide are formed on both sides of the resist layer for the lift off method. The formation of the anti-milling layers enables protection of the insulation layer (the upper gap layer) formed below the anti-milling layers from the ion milling in the subsequent step.
As shown in FIG. 5E, a resist layer 17 is provided in a recess 16a of a soft magnetic material layer 16. In this state, unidirectional ion milling can form the lower core layer in which the thickness gradually decreases toward the side ends, and the surfaces at the side ends become curved surfaces.
In this way, since the thickness of the shielding layer can be decreased toward the both side ends thereof, the shielding layer having a uniform thickness can be formed on the shielding layer. Also the formation of the anti-milling layers on the upper gap layer prevents the upper gap layer from being affected by ion milling and thus prevents breakage of the upper shielding layer.